1. Field of the Invention
A thermodynamic heat pump and heat engine system for selectively heating and cooling a target space, and more particularly such a thermodynamic system in which ambient air comprises the working fluid therefor.
2. Description of the Prior Art
Thermodynamic systems in the form of heat pumps are used in the prior art to alternatively heat or cool a target space in standard heating/cooling modes. Heat pumps generally include a compressor, two heat exchangers, and an expander all disposed in a common fluid flow path. Most heat pump systems are of the closed loop type in which the working fluid, typically a two-phase refrigerant, is circulated through the system so as to absorb heat through one of the heat exchangers and to reject heat from the other heat exchanger. When the target space is to be heated, the system is configured so that the heat exchanger that rejects heat will be stationed in the target space or in thermodynamic communication therewith such as via suitable plumping or ducting. Alternatively, when the target space is to be cooled, the system is configured so that the heat exchanger that rejects heat will be stationed in (or ducted to) the ambient environment or other suitable heat sink. Both configurations are considered within a standard heating/cooling mode. Not all heat pump systems are of the closed loop type; some heat pump systems have been proposed in an open-loop arrangement using ambient air as the working fluid.
A target space may be any enclosed or localized space. The target space may be a human environment, such as a building or the passenger compartment in an automobile. Alternatively, the target space may be a relatively small or large area for objects like a personal computer enclosure or a server room.
While such known heat pump systems are adequate in many climates, they are frequently unable to provide adequate heating during extremely cold conditions. This is because a typically sized system is not capable of cooling the working fluid (even in the case of a hazardous refrigerant) to a cold enough temperature so that it has capacity to absorb heat from an exceptionally cold ambient atmosphere. In these conditions, it may be necessary to supplement the heat pump with a secondary furnace, stove, or other heating apparatus to adequately heat the target space.
U.S. Pat. No. 3,686,893, issued to Thomas C. Edwards on Aug. 29, 1972 and U.S. Pat. No. 4,008,426, issued to Thomas C. Edwards on May 9, 1978 (hereinafter referred to as “the Edwards patents”), show a positive displacement rotating vane-type device that operates a thermodynamic cycle for simultaneously compressing and expanding a working fluid which may be air. The devices shown in the Edwards patents each have a stator housing and a rotor disposed in the stator housing defining an interstitial space therebetween. A plurality of vanes are operatively disposed between the rotor and the stator housing for dividing the interstitial space into revolving compression and expansion chambers. The vanes are spring loaded to slidably engage the inner wall of the stator housing. The rotor is rotatably disposed within the stator housing for rotating in a first direction. While the rotor is rotating, the vanes slide along the inner wall of the stator housing and simultaneously compress the working fluid in the compression chambers and expand the fluid in the expansion chambers.
The stator housing of the Edwards patents further define several ports for conducting the working fluid into and out of the device. These ports include a compression chamber inlet, a compression chamber outlet, an expansion chamber inlet, and an expansion chamber outlet. Additionally, the stator housing of the Edwards patents defines an expansion chamber inlet and an expansion chamber outlet. The compression chamber inlet and the expansion chamber outlet are both disposed on the side of the stator housing and communicate with different chambers. Thus, the working fluid enters and exits the device of the Edwards patents through various ports in a carefully arranged radial direction.
The Edwards patents are typical of prior art positive displacement rotating vane-type devices where the transfer of working fluid into and out of the device via ports is accomplished though localized piping that is arranged to prevent inadvertent mixing of high and low pressure fluids. Elaborate seals and other measures are sometimes taken to ensure the high and low pressure fluids never mix, and thereby reduce operating efficiencies. Such measures add considerably to the complexity and cost of positive displacement rotating vane-type devices.
There exists a need for further efficiency improvements in the field of heat pump systems, and more particularly for air-aspirated systems in which ambient air serves as the working fluid. There exists a need for a heat pump system that can fully meet the heating needs of a target space during very cold conditions. Furthermore, there exists a need for a heat pump system that is capable of efficiently transferring a working fluid (be it air or otherwise) between high and low pressure ports of a positive displacement rotating vane-type device without unnecessary complexity or cost.